Scott's Grubex should control grubs all season long so I don't think you need to apply the product a second time. You can test to see if your lawn has a large enough population of grubs to warrant additional treatment. Here's how: test specifically for grubs by cutting out one square foot of their turf. If you see five to ten grubs hanging from the roots, the lawn is lightly infested. Thirty to fifty grubs indicate a heavily infested lawn and a need to treat your lawn.

Several strains of the bacterium, Bacillus popilliae, called Milky Spore Disease, is a biological way to rid your lawn of grubs. Or insecticides such as imidacloprid (Merit) or halofenozide (GrubEx) can be applied to your lawn. Be sure to apply according to label directions.